The present invention relates to a gas sensor element and a gas sensor having the gas sensor element.
Hereinafter, the terms “front” and “rear” are used with respect to the axial direction of a gas sensor or the longitudinal direction of a solid electrolyte layer of the gas sensor for purposes of description. These terms are illustrative and are not intended to limit the scope of the present invention.
There has been used a gas sensor for combustion control of an internal combustion engine. The gas sensor includes a sensor element capable of outputting a detection signal responsive to the concentration of a specific gas component in gas under measurement, that is, exhaust gas flowing through an exhaust pipe of the internal combustion engine. Japanese Laid-Open Patent Publication No. 2010-38904 discloses one such type of sensor element that has a plate-shaped solid electrolyte layer formed predominantly of zirconia, a pair of electrodes arranged on a front side of the solid electrolyte layer, insulating layers formed on a rear side of the solid electrolyte layer and a pair of leads arranged on the insulating layers and connected to the electrodes, respectively, so as to generate a detection signal responsive to the concentration of the specific gas component (e.g. oxygen) in the exhaust gas in accordance with a potential difference developed between the electrodes by the exhaust gas and reference gas (air) and output the detection signal to an external control device. In this gas sensor element, it is necessary that each of the electrodes have a porous structure so as to take in and allow diffusion of the exhaust gas; whereas it is preferable that each of the leads has a dense structure so as to show low electrical resistance for use in signal transmission between the electrodes and the external control device.